Heat sensitive recording material

ABSTRACT

New crystal forms of N-(p-toluenesulphonyl)-N′-(3-p-toluenesulphonyl-oxy-phenyl)urea, methods for its manufacture, its use, in particular for the manufacture of heat sensitive recording materials.

The present invention relates to new crystal forms ofN-(p-toluenesulphonyl)-N′-(3-p-toluenesulphonyl-oxy-phenyl)urea, methodsfor their manufacture, their use and to heat sensitive recordingmaterials, comprising such new crystal forms.

WO 00/34567 describes novel heat sensitive recording materials as wellas novel color developers. One specific novel color developers concernsa compound of formula I

which isN-(p-toluenesulphonyl)-N′-(3-p-toluenesulphonyl-oxy-phenyl)urea. Whenmanufactured as described in WO 00/34567 the compound gives an X-raypowder pattern having Bragg angles (2θ/CuK_(α)) of 8.7, 9.7, 12.1, 12.5,13.8, 14.4, 16.8, 17.4, 18.4, 18.9, 19.6, 20.7, 21.2, 21.6, 23.4, 24.4,24.8, 25.2, 28.1, 28.8 (see FIG. 3).

Although the use of this compound in heat sensitive recording materialsproduces images with increased stability and at the same time improvesthe background whiteness of paper before and after ageing, still a needexists to improve even further the background whiteness of thermal paperboth before and after ageing under conditions of dry heat and thecombination of heat and moisture.

Hence, the present invention is directed toN-(p-toluenesulphonyl)-N′-(3-p-toluenesulphonyl-oxy-phenyl)urea havingan X-ray powder pattern having Bragg angles (2θ/CuK_(α)) of 10.3, 11.1,13.0, 13.3, 15.6, 17.1, 18.1, 18.4, 19.6, 20.0, 20.8, 21.3, 23.1, 25.0,25.5, 26.4, 26.8, 27.5, 29.1, 32.8; (main peak underlined), andN-(p-toluenesulphonyl)-N′-(3-p-toluenesulphonyl-oxy-phenyl)urea havingan X-ray powder pattern having Bragg angles (2θ/CuK_(α)) of 6.4, 8.1,10.1, 11.1, 12.0, 12.7, 13.7, 15.7, 16.2, 16.5, 18.0, 19.2, 19.9, 20.5,20.8, 21.3, 21.8, 22.4, 22.6, 23.1, 24.1, 25.1, 25.6, 26.5, 26.8, 27.7,28.6, 28.8, 32.1 (main peak underlined).

Further, the invention is directed to a method for manufacturing theabove novel compounds.

The novel compounds usually are obtained by treatingN-(p-toluenesulphonyl)-N′-(3-p-toluenesulphonyl-oxy-phenyl)urea obtainedaccording to example 4 of WO 00/34567 with a solvent for a period in therange of 1 to 100 hours at a temperature in the range of 0 to 150° C.,then isolatingN-(p-toluenesulphonyl)-N′-(3-p-toluenesulphonyl-oxy-phenyl)urea.

Hence, a further embodiment of this invention relates to a process,wherein N-(p-toluenesulphonyl)-N′-(3-p-toluenesulphonyl-oxy-phenyl)ureahaving an X-ray powder pattern having Bragg angles (2θ/CuK_(α)) of 8.7,9.7, 12.1, 12.5, 13.8, 14.4, 16.8, 17.4, 18.4, 18.9, 19.6, 20.7, 21.2,21.6, 23.4, 24.4, 24.8, 25.2, 28.1, 28.8 is treated with a solvent for aperiod in the range of 1 to 100 hours at a temperature in the range of 0to 150° C., followed by then re-crystallizingN-(p-toluenesulphonyl)-N′-(3-p-toluenesulphonyl-oxy-phenyl)urea.

This treatment can be incorporated in the isolation step of thesynthetic routes described in WO 00/35679 or maybe a post-isolationtreatment of the product obtained by the methods described in WO00/35679.

The solvent of choice maybe selected from the group consisting ofaromatic hydrocarbons, chlorinated aromatic hydrocarbons, aliphatic oralicyclic hydrocarbons, chlorinated hydrocarbons, dialkylacylamides,aliphatic esters, aliphatic ketones, alicyclic ketones, aliphaticethers, cyclic ethers, alkylnitriles or mixtures thereof. Most preferredare toluene, xylenes, petroleum ether, cyclohexane, dimethyl formamide,dimethylacetamide, ethylacetate, propyl acetate, butylacetate,diethylether, dibutylether, tetrahydrofuran, acetone, butanone,cyclohexanone, nitromethane, acetonitrile, propionitrile, nitromethane,ethyleneglycoldimethylether, chloroform, dichloromethane, carbontetrachloride, chlorobenzene, dichlorobenzene, dioxan or mixturesthereof.

In a preferred embodiment, toluene is chosen as solvent for themanufacture ofN-(p-toluenesulphonyl)-N′-(3-p-toluenesulphonyl-oxy-phenyl)urea havingan X-ray powder pattern having Bragg angles (2θ/CuK_(α)) of 10.3, 11.1,13.0, 13.3, 15.6, 17.1, 18.1, 18.4, 19.6, 20.0, 20.8, 21.3, 23.1, 25.0,25.5, 26.4, 26.8, 27.5, 29.1, 32.8, and ethyl acetate is chosen for themanufacture ofN-(p-toluenesulphonyl)-N′-(3-p-toluenesulphonyl-oxy-phenyl)urea havingan X-ray powder pattern having Bragg angles (2θ/CuK_(α)) of 6.4, 8.1,10.1, 11.1, 12.0, 12.7, 13.7, 15.7, 16.2, 16.5, 18.0, 19.2, 19.9, 20.5,20.8, 21.3, 21.8, 22.4, 22.6, 23.1, 24.1, 25.1, 25.6, 26.5, 26.8, 27.7,28.6, 28.8, 32.1.

Another embodiment of this invention relates to a mixture of colourdevelopers a) selected from the group consisting ofN-(p-toluenesulphonyl)-N′-(3-p-toluenesulphonyl-oxy-phenyl)urea havingan X-ray powder pattern having Bragg angles (2θ/CuK_(α)) of 10.3, 11.1,13.0, 13.3, 15.6, 17.1, 18.1, 18.4, 19.6, 20.0, 20.8, 21.3, 23.1, 25.0,25.5, 26.4, 26.8, 27.5, 29.1, 32.8, andN-(p-toluenesulphonyl)-N′-(3-p-toluenesulphonyl-oxy-phenyl)urea havingan X-ray powder pattern having Bragg angles (2θ/CuK_(α)) of 6.4, 8.1,10.1, 11.1, 12.0, 12.7, 13.7, 15.7, 16.2, 16.5, 18.0, 19.2, 19.9, 20.5,20.8, 21.3, 21.8, 22.4, 22.6, 23.1, 24.1, 25.1, 25.6, 26.5, 26.8, 27.7,28.6, 28.8, 32.1,

and b) N-(p-toluenesulphonyl)-N′-(3-toluenesulphonyl-oxy-phenyl)ureahaving an X-ray powder pattern having Bragg angles (2θ/CuK_(α)) of 8.7,9.7, 12.1, 12.5, 13.8, 14.4, 16.8, 17.4, 18.4, 18.9, 19.6, 20.7, 21.2,21.6, 23.4, 24.4, 24.8, 25.2, 28.1, 28.8.

A further preferred embodiment concerns the above mixture furthercomprising a compound of formula II

wherein

R¹ is C₁-C₂₀alkyl or C₆-C₁₀aryl, which can be substituted one to threetimes with halogen, C₁-C₄alkyl, —NR²R³, wherein R² and R³ independentlyfrom each other stand for hydrogen or C₁-C₈alkyl, or C₁-C₈acyl amino.

A further embodiment of this invention relates to a heat sensitiverecording material, comprising the inventive compounds or inventivemixtures.

A preferred embodiment of this invention relates to the above heatsensitive material further comprising at least one colour formingcompound.

The colour forming compounds are, for example, triphenylmethanes,lactones, benzoxazines, spiropyrans or preferably fluorans.

Preferred colour formers include but are not limited to:3-diethylamino-6-methylfluoran,3-dimethylamino-6-methyl-7-anilinofluoran,3-diethylamino-6-methyl-7-anilinofluoran,3-diethylamino-methyl-7-(2,4-dimethylanilino)fluoran,3-diethylamino-6-methyl-7-chlorofluoran,3-diethylamino-6-methyl-7-(3-trifluoromethylanilino)fluoran,3-diethylamino-6 methyl-7-(2-chloroanilino)fluoran,3-diethylaminomethyl-7-(4-chloroanilino)fluoran,3-diethylamino-6-methyl-7-(2-fluoroanilino)fluoran,3-diethylamino-6-methyl-7-(4-n-octylanilino) fluoran,3-diethylamino-7-(4-n-octylanilino)fluoran,3-diethylamino-7-(n-octylamino)fluoran,3-diethylamino-7-(dibenzylamino)fluoran,3-diethylamino-6-methyl-7-(dibenzylamino) fluoran,3-diethylamino-6-chloro-7-methylfluoran,3-diethylamino-7-t-butylfluoran, 3-diethylamino-7-carboxyethylfluoran,3-diethylamino-6-chloro-7-anilinofluoran,3-diethylamino-6-methyl-7-(3-methylanilino)fluoran,3-diethylamino-6-methyl-7-(4-methylanilino) fluoran,3-diethylamino-6-ethoxyethyl-7-anilinofluoran,3-diethylamino-7-methylfluoran, 3-diethylamino-7-chlorofluoran,3-diethylamino-7-(3-trifluoromethylanilino) fluoran,3-diethylamino-7-(2-chloroanilino)fluoran,3-diethylamino-7-(2-fluoroanilino)fluoran,3-diethylamino-benzo[a]fluoran, 3-diethylamino-benzo[c]fluoran,3-dibutylamino-7-dibenzylaminofluoran, 3-dibutylamino-7-anilinofluoran,3-diethylamino-7-anilinofluoran, 3-dibutylamino-6-methyl fluoran,3-dibutylamino-6-methyl-7-anilinofluoran,3-dibutylamino-6-methyl-7-(2,4-dimethylanilino) fluoran,3-dibutylamino-6-methyl-7-(2-chloroanilino) fluoran,3-dibutylamino-6-methyl-7-(4-chloroanilino)fluoran,3-dibutylamino-6-methyl-7-(2-fluoroanilino) fluoran,3-dibutylamino-6-methyl-7-(3-trifluoromethylanilino)fluoran,3-dibutylamino-6-ethoxyethyl-7-anilinofluoran,3-dibutylamino-6-chloro-anilinofluoran,3-dibutylamino-6-methyl-7-(4-methylanilino)fluoran,3-dibutylamino-7-(2-chloroanilino)fluoran,3-dibutylamino-7-(2-fluoroanilino) fluoran,3-dibutylamino-7-(N-methyl-N-formylamino)fluoran,3-dipentylamino-methyl-7-anilinofluoran,3-dipentylamino-6-methyl-7-(2-chloroanilino)fluoran,3-dipentylamino-7-(3-trifluoromethylanilino)fluoran,3-dipentylamino-6-chloro-7-anilinofluoran,3-dipentylamino-7-(4-chloroanilino)fluoran,3-pyrrolidino-6-methyl-7-anilinofluoran,3-piperidino-methyl-7-anilinofluoran,3-(N-methyl-N-propylamino)-6-methyl-7-anilinofluoran,3-(N-methyl-N-cyclohexylamino)-6-methyl-7-anilinofluoran,3-(N-ethyl-N-cyclohexylamino)-6-methyl-7-anilinofluoran,3-(N-ethyl-p-toluidino)-6-methyl-7-anilinofluoran,3-(N-ethyl-N-isoamylamino)-6-methyl-7-anilinofluoran,3-(N-ethyl-N-isoamylamino)-6-chloro-7-anilinofluoran,3-(N-ethyl-N-tetrahydrofurfurylamino)+methyl-7-anilinofluoran,3-(N-ethyl-N-isobutylamino)-6-methyl-7-anilinofluoran,3-(N-butyl-N-isoamylamino)-6-methyl-7-anilinofluoran,3-(N-isopropyl-N-3-pentylamino-6-methyl-7-anilinofluoran,3-(N-ethyl-N-ethoxypropylamino)-6-methyl-7-anilinofluoran,3-cyclohexylamino-6-chlorofluoran,2-methyl-6-p-(p-dimethylaminophenyl)aminoanilinofluoran,2-methoxy-6-p-(p-dimethylaminophenyl)-aminoanilinofluoran,2-chloro-3-methyl-6-p-(p-phenylaminophenyl)aminoanilinofluoran,2-diethylamino-6-p-(p-dimethylaminophenyl)aminoanilinofluoran,2-phenyl-6-methyl-6-p-(p-phenylaminophenyl)aminoanilinofluoran,2-benzyl-6-p-(p-phenylaminophenyl)amino-anilinofluoran,3-methyl-6-p-(p-dimethylaminophenyl)aminoanilinofluoran,3-diethylamino-6 p-(p-diethylaminophenyl)aminoanilinofluoran,3-diethylamino-6-p-(p-dibutylaminophenyl) aminoanilinofluoran,2,4-dimethyl-6-[(4-dimethylamino)anilino]fluoran,3-[(4-dimethyl-aminophenyl)amino]-5,7-dimethylfluoran,3,6,6′-tris(dimethylamino)spiro[fluorene-9,3′-phthalide],3,6,6′-tris(diethylamino)spiro[fluorene-9,3′-phthalide],3,3-bis(p-dimethylamino-phenyl)-6-dimethylaminophthalide,3,3-bis(p-dimethylaminophenyl)phthalide,3,3-bis-[2-(p-dimethylaminophenyl)-2-(p-methoxyphenyl)ethenyl-4,5,6,7-tetrabromophthalide,3,3-bis-[2-(p-dimethylaminophenyl)2-(p-methoxyphenyl)ethenyl-4,5,6,7-tetrachlorophthalide,3,3-bis[1,1-bis(4-pyrrolidinophenyl)ethylene-2-yl]-4,5,6,7-tetrabromophthalide,3,3-bis-[1-(4-methoxyphenyl)-1-(4-pyrridinophenyl)ethylene-2-yl]-4,5,6,7-tetrachlorophthalide,3-(4diethylamino-2-ethoxyphenyl)-3-(1-ethyl-2-methylindole-3-yl)-4-azaphthalide,3-(4diethylamino-2-ethoxyphenyl)-3-(1-octyl-2-methylindole-3-yl)-4-azaphthalide,3-(4cyclohexylethylamino-2-methoxyphenyl)-3-(1-ethyl-2-methylindole-3-yl)-4-azaphthalide,3,3-bis(1-ethyl-2-methylindole-3-yl) phthalide,3,3-bis(1-octyl-2-methylindole-3-yl) phthalide, mixture of2-phenyl-(4-diethylaminophenyl)-4-(4-methoxyphenyl)-6-methyl-7-dimethylamino-3,1-benzoxazineand2-phenyl-4-(4-diethylaminophenyl)-4-(4-methoxyphenyl)-8-methyl-7-dimethylamino-3,1-benzoxazine,4,4′-[1-methylethylidene)bis(4,1-phenyleneoxy-4,2-quinazolinediyl)]bis[N,N-diethylbenzenamine],bis(N-methyldiphenylamine)-4-yl-(N-butylcarbazole)-3-yl-methane,3-diethylamino-6,8-dimethylfluoran, 3-diethylamino-7,8-benzofluoran,3-diethylaminofluoran-7-carboxylic acid ethyl ester,3-[N-(4-methylphenyl)-N-ethylamino]-7-methylfluoran, and mixturesthereof.

All of the above colour forming compounds can be used singly or as amixture with other colour forming compounds; or they may also be usedtogether with further black colour forming compounds.

Highly preferred are 3-diethylamino-6-methyl-7-anilinofluoran,3-diethylamino-6-methyl-7-(3-methylanilino) fluoran,3-diethylamino-6-methyl-7-(2,4-dimethylanilino)fluoran,3-dibutylamino-6-methyl-7-anilinofluoran,3-dipentylamino-6-methyl-7-anilinofluoran,3-(N-methyl-N-propylamino)-6-methyl-7-anilinofluoran,3-(N-methyl-N-cyclohexylamino)-6-methyl-7-anilinofluoran,3-(N-ethyl-N-isoamylamino)-6-methyl-7-anilinofluoran,3-diethylamino-6-chloro-7-anilinofluoran,3-dibutylamino-7-(2-chloroanilino)fluoran,3-N-ethyl-p-toluidino-6-methyl-7-anilinofluoran,3-(N-ethyl-N-tetrahydrofurfurylamino)-6-methyl-7-anilinofluoran,3-(N-ethyl-N-isobutylamino)-6-methyl-7-anilinofluoran,3-N-ethyl-N-ethoxypropylamino-6-methyl-7-anilinofluoran,2,4-dimethyl-6-[(4-dimethylamino)anilino]fluoran,3-(4-diethylamino-2-ethoxyphenyl)-3-(1-octyl-2-methylindole-3yl)-4-azaphthalide,3,3-bis(p-dimethylamino-phenyl)-6-dimethylaminophthalide and mixturesthereof.

It is also possible to use solid solutions comprising at least twocolour forming compounds.

A monophase (or single-phase or guest-host) solid solution possesses acrystal lattice which is identical with the crystal lattice of one ofits components. One component is embedded as the ‘guest’ in the crystallattice of the other component, which acts as the ‘host’. The X-raydiffraction pattern of such a monophase solid solution is substantiallyidentical to that of one of the components, called the ‘host’. Withincertain limits, different proportions of the components produce almostidentical results.

In the literature, the definitions by the various authors, such as, G.H. Van't Hoff, A. I. Kitaigorodsky and A. Whitacker for solid solutionsand mixed crystals are often contradictory, (cf, e.g. ‘AnalyticalChemistry of Synthetic Dyes’, Chapter 10/page 269, Editor K.Venkataraman, J. Wiley, New York, 1977).

The term ‘monophase solid solution’ or ‘multiphase solid solution’ ormixed crystal’, as defined herein, therefore, should be taken from thefollowing definitions, which have been adapted to the current improvedstate of knowledge of such systems: A monophase (or single-phase orguest-host) solid solution possesses a crystal lattice which isidentical with the crystal lattice of one of its components. Onecomponent is embedded as the ‘guest’ in the crystal lattice of the othercomponent, which acts as the ‘host’. The X-ray diffraction pattern ofsuch a monophase solid solution Is substantially identical to that ofone of the components, called the ‘host’. Within certain limits,different proportions of the components produce almost identicalresults.

A multiphase solid solution possesses no precise, uniform crystallattice. It differs from a physical mixture of its components in thatthe crystal lattice of at least one of its components is partially orcompetely altered. In comparison to a physical mixture of thecomponents, which gives an X-ray diffraction diagram that is additive ofthe diagrams seen for the individual components. The signals in theX-ray diffraction diagram of a multiphase solid solution are broadened,shifted or altered in intensity. In general, different proportions ofthe components produce different results.

A mixed crystal (or solid compound type) solid solution possesses aprecise composition and a uniform crystal lattice, which is differentfrom the crystal lattices of all its components. If differentproportions of the components lead, within certain limits, to the sameresult, then a solid solution is present in which the mixed crystal actsas a host.

For the avoidance of doubt it may also be pointed out that, inter alia,there may also be amorphous structures and mixed aggregates consistingof different particles of different physical type, such as, for example,an aggregate of different components each in pure crystal modification.Such amorphous structures and mixed aggregates cannot be equated witheither solid solutions or mixed crystals, and possess differentfundamental properties.

As hereinbefore detailed, the monophase solid solutions comprise aplurality of colour compounds. Suitable colour forming materials whichmay be included in the solid solutions are those given above.

Of particular interest are the following monophase solid solutions:

3-dibutylamino-6-methyl-7-anilinofluoran and3-dibutylamino-7-dibenzylaminofluoran;3-dibutylamino-6-methyl-7-anilinofluoran and3-dibutylamino-7-anilinofluoran;3-dibutylamino-6-methyl-7-anilinofluoran and3-diethylamino-7-anilinofluoran;3-diethylamino-6-methyl-7-anilinofluoran and3-diethylamino-7-anilinofluoran;3-dibutylamino-6-methyl-7-anilinofluoran and3-diethylamino-6-methyl-7-anilinofluoran;3-dibutylamino-6-methyl-7-anilinofluoran and3-N-isoamyl-N-ethylamino-6-methyl-7-anilinofluoran;3-dibutylamino-6-methyl-7-anilinofluoran and3-N-2-pentyl-N-ethylamino-6-methyl-7-anilinofluoran;3-dibutylamino-6-methyl-7-anilinofluoran and3-N-isopropyl-N-ethylamino-6-methyl-7-anilinofluoran;3-dibutylamino-6-methyl-7-anilinofluoran and3-N-Cyclohexylmethyl-N-ethylamino-6-methyl-7-anilinofluoran;3-dibutylamino-6-methyl-7-anilinofluoran and3-dipropylamino-6-methyl-7-anilinofluoran;3-dibutylamino-6-methyl-7-anilinofluoran and3-N-2-butyl-N-ethylamino-6-methyl-7-anilinofluoran;3-dibutylamino-6-methyl-7-anilinofluoran and3-N-cyclohexyl-N-methylamino-6-methyl-7-anilinofluoran;3-dibutylamino-6-methyl-7-anilinofluoran and3-diethylamino-6-methyl-7-(3-methylanilino)fluoran;3-dibutylamino-6-methyl-7-anilinofluoran and3-diethylamino-6-methyl-7-(2,4-dimethylanilino)fluoran;3-dibutylamino-6-methyl-7-anilinofluoran and3-dipentylamino-6-methyl-7-anilinofluoran;3-dibutylamino-6-methyl-7-anilinofluoran and3-(N-methyl-N-propylamino)-6-methyl-7-anilinofluoran; 3-dibutylamino-6methyl-7-anilinofluoran and 3-diethylamino-6-chloro-7-anilinofluoran;3-dibutylamino-6-methyl-7-anilinofluoran and3-dibutylamino-7-(2-chloroanilino)fluoran; 3-dibutylamino-6methyl-7-anilinofluoran and3-N-ethyl-p-toluidino-6-methyl-7-anilinofluoran;3-dibutylamino-6-methyl-7-anilinofluoran and3-(N-ethyl-N-tetrahydrofurfurylamino)-6-methyl-7-anilinofluoran;3-dibutylamino-6-methyl-7-anilinofluoran and3-(N-ethyl-N-isobutylamino)+methyl-7-anilinofluoran;3-dibutylamino-6-methyl-7-anilinofluoran and3-N-ethyl-N-ethoxypropylamino-6-methyl-7-anilinofluoran;3-dibutylamino-6-methyl-7-anilinofluoran and2,4-dimethyl-6-[(4-dimethylamino)anilino]fluoran;3N-isoamyl-N-ethylaminomethyl-7-anilinofluoran and3-diethylamino-6-methyl-7-anilinofluoran;3-diethylaminomethyl-7-anilinofluoran and3N-propyl-N-methylamino-6-methyl-7-anilinofluoran;3-diethylamino-6-methyl-7-(3-tolyl)aminofluoran and3-diethylamino-6-methyl-7-anilinofluoran;3-dibutylamino-6-methyl-7-anilinofluoran and3,3-bis(1-octyl-2-methylindol-3-yl)phthalide;3-dibutylamino-6-methyl-7-anilinofluoran and mixture of2-phenyl-4-(4-diethylaminophenyl)-4-(4-methoxyphenyl)-6-methyl-7-dimethylamino-3,1-benzoxazineand 2-phenyl-4-(4-diethylaminophenyl)-4-(4methoxyphenyl)-6-methyl-7-dimethylamino-3,1-benzoxazine;3-dibutylamino-6-methyl-7-anilinofluoran and4,4′-[1-methylethylidene)bis(4,1-phenyleneoxy-4,2-quinazoline-diyl)]bis[N,N-diethylbenzenamine].

In the above monophase solid solutions the first compound is in a molarratio of 75 to 99.9% by mole, the second compound is in a ratio of 25 to0.1% by mole.

Examples of monophase solid solutions comprising two components A and Bin the stated ratios are: 3-dibutylamino-6-methyl-7-anilinofluoran(99.9%), 3-diethylamino-6-methyl-7-anilinofluoran (0.1%);3-dibutylamino-6-methyl-7-anilinofluoran (99%),3-diethylamino-6-methyl-7-anilinofluoran (1%);3-dibutylamino-6-methyl-7-anilinofluoran (95%),3-diethylamino-6-methyl-7-anilinofluoran (5%);3-dibutylamino-6-methyl-7-anilinofluoran (90%) and3-N-2-pentyl-N-ethylaminomethyl-7-anilinofluoran (10%);3-dibutylamino-6-methyl-7-anilinofluoran (95%) and3-N-2-pentyl-N-ethylamino-6-methyl-7-anilinofluoran (5%);3-dibutylamino-6-methyl-7-anilinofluoran (90%) and3-N-isopropyl-N-ethylamino-6-methyl-7-anilinofluoran (10%);3-dibutylamino-6-methyl-7-anilinofluoran (95%) and3-N-isopropyl-N-ethylamino-methyl-7-anilinofluoran (5%);3-dibutylamino-6-methyl-7-anilinofluoran (90%) and3-N-Cyclohexylmethyl-N-ethylamino-6-methyl-7-anilinofluoran (10%);3-dibutylamino-6-methyl-7-anilinofluoran (95%) and3-N-Cyclohexylmethyl-N-ethylamino-6-methyl-7-anilinofluoran (5%);3-dibutylamino-6-methyl-7-anilinofluoran (90%) and3-dipropylamino-6-methyl-7-anilinofluoran (10%);3-dibutylamino-6-methyl-7-anilinofluoran (95%) and3-dipropylamino-6-methyl-7-anilinofluoran (5%);3-dibutylamino-6-methyl-7-anilinofluoran (90%) and3-N-2-butyl-N-ethylamino-6-methyl-7-anilinofluoran (10%);3-dibutylamino-6-methyl-7-anilinofluoran (95%) and3-N-2-butyl-N-ethylamino-6-methyl-7-anilinofluoran (5%);3-dibutylamino-6-methyl-7-anilinofluoran (90%),3-diethylamino-6-methyl-7-anilinofluoran (10%);3-dibutylamino-6-methyl-7-anilinofluoran (85%),3-diethylamino-6-methyl-7-anilinofluoran (15%);3-dibutylamino-6-methyl-7-anilinofluoran (80%),3-diethylamino-6-methyl-7-anilinofluoran (20%);3-dibutylamino-6-methyl-7-anilinofluoran (95%),3-N-isoamyl-N-ethylamino-6-methyl-7-anilinofluoran (5%);3-dibutylamino-6-methyl-7-anilinofluoran (90%),3-N-isoamyl-N-ethylamino-6-methyl-7-anilinofluoran (10%);3-dibutylamino-6-methyl-7-anilinofluoran (80%),3-N-isoamyl-N-ethylamino-6-methyl-7-anilinofluoran (20%);3-dibutylamino-6-methyl-7-anilinofluoran (90%),3-N-cyclohexyl-N-methylamino-6-methyl-7-anilinofluoran (10%);3-diethylamino-6-methyl-7-anilinofluoran (90%),3-N-isoamyl-N-ethylamino-6-methyl-7-anilinofluoran (10%);3-diethylamino-6-methyl-7-anilinofluoran (80%),3-N-isoamyl-N-ethylamino-6-methyl-7-anilinofluoran (20%);3-diethylamino-6-methyl-7-anilinofluoran (20%),3-N-isoamyl-N-ethylamino-6-methyl-7-anilinofluoran (80%);3-diethylamino-6-methyl-7-anilinofluoran (10%),3-N-isoamyl-N-ethylamino-6-methyl-7-anilinofluoran (90%);3-diethylamino-6-methyl-7-anilinofluoran (90%),3-N-propyl-N-methylamino-6-methyl-7-anilinofluoran (10%);3-diethylamino-6-methyl-7-anilinofluoran (80%),3-N-propyl-N-methylamino-6-methyl-7-anilinofluoran (20%);3-diethylamino-6-methyl-7-anilinofluoran (20%),3-N-propyl-N-methylamino-6-methyl-7-anilinofluoran (80%);3-diethylamino-6-methyl-7-anilinofluoran (10%),3-N-propyl-N-methylamino-6-methyl-7-anilinofluoran (90%);3-diethylamino-6-methyl-7-anilinofluoran (10%), 3-diethylamino-6methyl-7-(3-tolyl)aminofluoran (90%);3-diethylamino-6-methyl-7-anilinofluoran (20%),3-diethylamino-methyl-7-(3-tolyl)aminofluoran (80%);3-dibutylamino-6-methyl-7-anilinofluoran (90%),3,3-bis(1-octyl-2-methylindol-3-yl)phthalide (10%);3-dibutylamino-6-methyl-7-anilinofluoran (80%),3,3-bis(1-octyl-2-methylindol-3-yl)phthalide(20%);3-dibutylamino-6-methyl-7-anilinofluoran (90%), mixture of2-phenyl-4-(4-diethylaminophenyl)-4-(4-methoxyphenyl)-6-methyl-7-dimethylamino-3,1-benzoxazineand2-phenyl-4-(4-diethylaminophenyl)-4-(4-methoxyphenyl)-8-methyl-7-dimethylamino-3,1-benzoxazine(10%);3-dibutylamino-6-methyl-7-anilinofluoran (80%), mixture of2-phenyl(4-diethylamino-phenyl)-4-(4-methoxyphenyl)-6-methyl-7-dimethylamino-3,1-benzoxazineand 2-phenyl(4diethylaminophenyl)-4-(4-methoxyphenyl)-8-methyl-7-dimethylamino-3,1-benzoxazine(20%);3-dibutylamino-6-methyl-7-anilinofluoran (90%),4,4′-[1-methylethylidene)bis(4,1-phenylene-oxy-4,2-quinazolinediyl)]bis[N,N-diethylbenzenamine](10%);3-dibutylamino-6-methyl-7-anilinofluoran (80%),4,4′-[1-methylethylidene)bis(4,1-phenyleneoxy-4,2-quinazolinediyl)]-bis[N,N-diethylbenzenamine](20%).

The monophase solid solutions can be used singly or as a mixture withother colour forming compounds such as triphenylmethanes, lactones,fluorans, benzoxazines and spiropyrans; or they may also be usedtogether with further black colour forming compounds. Examples of suchother colour forming compounds are given hereinbefore.

The monophase solid solutions can be prepared by a variety of methods.One such method is the recrystallisation method wherein a physicalmixture of the desired components is dissolved, with or without heating,in a suitable solvent or solvent mixture. Suitable solvents include butare not limited to toluene, benzene, xylene, dichlorobenzene,chlorobenzene, 1,2-dichloroethane, methanol, ethanol, iso-propanol,n-butanol, acetonitrile, dimethylformamide or mixtures of these solventswith each other and with water. The monophase solid solution is thenisolated by crystallisation from the solvent or solvent mixture. Thiscan be brought about by cooling, standing, addition of a further solventto promote crystallisation or concentration by standard means such asdistillation, steam distillation and vacuum distillation. When themonophase solid solution is isolated by concentration it may beadvantageous to do so in the presence of a small amount of base, toimprove the visual aspect of the isolated product.

Alternatively, monophase solid solutions can be prepared from mixturesof the appropriate starting materials. The technique can be used toproduce mixtures of two or more fluorans or phthalides. For example,mixtures of two fluorans are produced by replacing a single startingmaterial with two analogous materials to the same total molarconcentration in the reaction. In the case of fluorans, these startingmaterials are derivatives of amino phenols, phthalic anhydrides, ketoacids and diphenylamines.

In addition, the heat sensitive recording material can contain apreviously known developer, unless the colour forming performance of theresultant heat sensitive material is disturbed thereby. Such developersare exemplifed by but not limited to; 4,4′-isopropylidene bisphenol,4,4′-sec-butylidene bisphenol, 4,4′-cyclohexylidene bisphenol,2,2-bis-(4-hydroxyphenyl)-4 methylpentane,2,2-dimethyl-3,3-di(4-hydroxyphenyl)butane, 2,2′-dihydroxydiphenyl,1-phenyl-1,1-bis(4-hydroxyphenyl)butane,4-phenyl-2,2-bis(4-hydroxyphenyl)butane,1-phenyl-2,2-bis(4-hydroxyphenyl)butane,2,2-bis(4′-hydroxy-3′-methylphenyl)-4-methylpentane,2,2-bis(4′-hydroxy-3′-tert-butyl]phenyl)-4-methylpentane,4,4′-sec-butylidene-bis(2-methylphenol),4,4′-isopropylidene-bis(2-tert-butylphenol),2,2-bis(4′-hydroxy-3′-isopropylphenyl)-4-methylpentane,allyl-4,4-bis(4′-hydroxyphenyl)pentanoate,propargyl-4,4-bis(4′-hydroxyphenyl)pentanoate,n-propyl-4,4-bis(4′-hydroxyphenyl)pentanoate, 2,4-bis(phenylsulfonyl)phenol, 2-(4-methylsulfonyl)-4-(phenylsulfonyl)phenol,2-(phenylsulfonyl)-4-(4-methylsulfonyl)phenol,2,4-bis(4-methylphenylsulfonyl)phenol,pentamethylene-bis(4-hydroxybenzoate),2,2-dimethyl-3,3-di(4-hydroxyphenyl)pentane,2,2-di(4-hydroxyphenylhexane, 4,4′-dihydroxydiphenyl thioether,1,7-di(4-hydroxyphenylthio)-3,5-dioxaheptane,2,2′-bis(4-hydroxyphenylthio)diethyl ether,4,4′-dihydroxy-3,3′-dimethylphenyl thioether; benzyl-4-hydroxybenzoate,ethyl-4-hydroxybenzoate, propyl-hydroxybenzoate,isopropyl-4-hydroxybenzoate, butyl-4-hydroxybenzoate,isobutyl-4-hydroxybenzoate, 4,4′-dihydroxydiphenyl sulfone,2,4′-dihydroxydiphenyl sulfone, 4-hydroxy-4′-methyldiphenyl sulfone,4-hydroxy-4′-isopropoxydiphenyl sulfone, 4-hydroxy-4′-butoxydiphenylsulfone, 4,4′-dihydroxy-3,3′-diallyldiphenyl sulfone,3,4-dihydroxy-4′-methyldiphenyl sulfone,4,4′-dihydroxy-3,3′,5,5′-tetrabromodiphenyl sulfone,4,4′-bis(p-toluenesulphonylamino-carbonylamino) diphenylmethane,N-p-toluenesulphonyl-N′-phenyl urea, dimethyl 4-hydroxyphthalate,dicyclohexyl 4-hydroxyphthalate, diphenyl 4-hydroxyphthalate,4-[2-(4-methoxyphenyloxy)ethyloxy]salicylate, 3,5-di-tert-butylsalicylicacid, 3-benzyl salicylic acid, 3-(α-methylbenzyl) salicylic acid,3-phenyl-5-(α,α-dimethylbenzyl) salicylic acid, 3,5-di-α-methylbenzylsalicylic acid; metal salts of salicylic acid, 2-benzylsulfonylbenzoicacid, 3-cyclohexyl-4-hydroxybenzoic acid, zinc benzoate, zinc4-nitrobenzoate, 4-(4′-phenoxy-butoxy)phthalic acid,4-(2′-phenoxyethoxy)phthalic acid, 4-(3′-phenylpropyloxy)phthalic acid,mono(2-hydroxyethyl)-5-nitro-isophthalic acid, 5-benzyloxycarbonylisophthalic add, 5-(1′-phenylethanesulfonyl)isophthalic acid,bis(1,2-dihydro-1,5-dimethyl-2-phenyl-3H-pyrazol-3-one-O)bis(thiocyanato-N)zinc, zinc bis[4-n-octyloxycarbonylamino)salicylate]dihydrate,4-hydroxybenzoate ester derivative (manufactured by Asahi Denka Kogyounder the trade-name ADEKA ARKLS K-5®) and mixtures thereof.

In addition, the heat sensitive recording material of the invention cancontain at least one stabiliser.

Representative stabilisers for use in the inventive heat sensitiverecording materials are selected from the group consisting of2,2′-methylene-bis(4-methyl-tert-butylphenol),2,2′-methylene-bis(4-ethyl-6-tert-butylphenol),4,4′-butylidene-bis(3-methyl-6-tert-butylphenol),4,4′-thio-bis(2-tert-butyl-5-methylphenol),1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane,1,1,3-tris(2-methyl-4-hydroxy-5-cyclohexylphenyl)butane,bis(3-tert-butyl-4-hydroxy-6-methylphenyl)sulfone,bis(3,5-dibromo-4-hydroxyphenyl)sulfone, 4,4′-sulfinylbis(2-tert-butyl-5-methylphenol), 2,2′-methylenebis(4,6-di-tert-butylphenyl)phosphate and alkali metal, ammonium andpolyvalent metal salts thereof, 4-benzyloxy-4′-(2-methylglycidyloxy)diphenyl sulfone, 4,4′-diglycidyloxydiphenyl sulfone,1,4-diglydidyloxybenzene, 4-[α-(hydroxymethyl)benzyloxy]-hydroxydiphenylsulfone, metal salts of p-nitrobenzoic acid, metal salts of phthalicacid mono benzyl ester, metal salts of cinnamic acid and mixturesthereof.

Preferred stabilisers are4,4′-butylidene-bis(3-methyl-6-tert-butylphenol),4,4′-thio-bis(2-tert-butyl-5-methylphenol),1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane,1,1,3-tris(2-methyl-4-hydroxy-5-cyclohexylphenyl)butane,4-benzyloxy-4′-(2-methylglycidyloxy)diphenyl sulfone and mixturesthereof.

The heat sensitive recording material of the invention can be preparedaccording to conventional methods. For example, at least one colourforming compound, at least one colour developer and, if desired, atleast one sensitiser are pulverised separately in water or a suitabledispersing medium such as aqueous polyvinyl alcohol by means of a ballmill, an attritor, a sand mill or like pulveriser to form an aqueous orother dispersion with an average particle diameter of about 0.2 to 2.0μm.

The fine particle dispersions thus obtained are combined and then mixedwith conventional amounts of binder, pigment, lubricant and, if desired,a stabiliser and/or one or more auxiliaries, and the resulting mixtureis stirred to obtain a heat sensitive recording layer composition. Thecoating composition is applied to a support and the resulting coating isdried. The system of the invention can be employed for other end useapplications using colour forming materials, for example, a temperatureindicating material.

The support can be a variety of suitable supports used in this field,and examples thereof include paper, wood-free paper made fromnon-chlorine bleached pulp, base paper containing waste paper plasticfilms, and synthetic paper.

Representative binders for use in the heat sensitive recording layerinclude polyvinyl alcohol (fully or partially hydrolysed),carboxy-modified polyvinyl alcohol, acetoacetyl-modified polyvinylalcohol, diacetone-modified polyvinyl alcohol, silicon-modifiedpolyvinyl alcohol, oxidised starch, gelatine, caesin, derivatives ofcellulose such as hydroxyethyl cellulose, methyl cellulose, ethylcellulose, carboxymethyl cellulose and acetyl cellulose, starch-vinylacetate graft copolymers, styrene-maleic anhydride copolymers, methylvinyl ether-maleic anhydride co-polymers, isopropylene-maleic anhydridecopolymers and like water-soluble resins, styrene-butadiene latex,acrylic latex, urethane latex and like water-dispersible resins andmixtures thereof. The amount of the binder to be used is about 5 to 40weight-%, preferably about 7 to 30% b.w., based on the heat sensitiverecording layer.

Representative pigments for use in the heat sensitive recording layerinclude ground calcium carbonate, precipitated calcium carbonate,kaolin, calcined kaolin, aluminium hydroxide, talc, titanium dioxide,zinc oxide, amorphous silica, barium sulfate, polystyrene resin,urea-formaldehyde resin, hollow plastic pigment and mixtures thereof.The amount of pigment to be used is about 5 to 75 weight-%, preferablyabout 10 to 60 weight-% based on the heat sensitive recording layer.

Representative lubricants for use in the heat sensitive recording layerinclude stearamide, methylene bis stearamide, polyethylene wax, carnaubawax, paraffin wax, zinc stearate, calcium stearate and mixtures thereof.

Examples of various auxiliaries that can be added to the heat sensitivelayer coating composition, if so desired, include surfactants such assodium dioctylsulfosuccinate, sodium dode-cybenzenesulfonate, sodiumlauryl sulfate and fatty acid metal salts; insolubilisers such asglyoxal, urea-formaldehyde resins, melamine-formaldehyde resins,polyamide resins, polyamideamine-epichlorohydrin resins, adipic aciddihydrazide, boric acid, borax, ammonium zirconium carbonate andpotassium zirconium carbonate; antifoaming agents, fluorescent whiteningagents, fluorescent dyes and/or pigments, tinting dyes and UV absorbers.

The ultraviolet absorbers may be employed in either the thermosensitivecolouring layer or in a protective layer, and if desired, may be used inmicroencapsulated form in the protective layer.

Representative examples of ultraviolet absorbers that may be used in theinvention include phenyl salicylate, p-tert-butylphenyl salicylate,p-octylphenyl salicylate and like salicylic acid type ultravioletabsorbers:

-   2,4-Dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone,    2-hydroxy-4-octyloxybenzophenone,    2-hydroxy-4-dodecyloxybenzophenone, 2,2′-dihydroxy-4    methoxybenzophenone, 2,2′-dihydroxy-4,4′-dimethoxybenzophenone,    2-hydroxy-4-methoxy-5-sulfobenzophenone and like benzophenone type    ultraviolet absorbers;-   2-ethylhexyl-2-cyano-3,3-diphenylacrylate,    ethyl-2-cyano-3,3-diphenylacrylate and like cyanoacrylate type    ultraviolet absorbers; bis(2,2,6,6-tetramethyl-4-piperidyl)    sebacate, bis(2,2,6,6-tetramethyl-4-piperidyl) succinate,    bis(1,2,2,6,6-pentamethyl-4-piperidyl)-2-(3,5-di-tert-butyl-4-hydroxybenzyl)-2-n-butyl    malonate and like hindered amine type ultraviolet absorbers;-   2-(2′-Hydroxyphenyl)benzotriazole,    2-(2′-hydroxy-5′-methylphenyl)benzotriazole,    2-(2′-hydroxy-5′-tert-butylphenyl)benzotriazole,    2-(2′-hydroxy-3,5′-di-tert-butylphenyl)benzotriazole,    2-(2′-hydroxy-3′-tert-butyl-5′-methylphenyl)-5-chlorobenzotriazole,    2-(2′-hydroxy-3,5′-di-tert-butylphenyl)-5-chlorobenzotriazole,    2-(2′-hydroxy-3,5′-di-tert-butylphenyl)-S-tert-butylbenzotriazole,    2-(2′-hydroxy-3,5′-di-tert-amylphenyl)benzotriazole,    2-2′-hydroxy-3,5-di-tert-amylphenyl)-5-tert-amylbenzotriazole,    2-(2′-hydroxy-3,5′-di-tert-amylphenyl) 5 methoxybenzotriazole,    2-[2′-hydroxy-3′-(3″,4″,5″,6″-tetrahydrophthalimido-methyl)-5′-methylphenyl]benzotriazole,    2-(2′-hydroxy-5′-tert-octylphenyl)benzotriazole,    2-(2′-hydroxy-3′-sec-butyl-5′-tert-butylphenyl)benzotriazole,    2-2′-hydroxy-3′-tert-amyl-5′-phenoxyphenyl)-5-methylbenzotriazole,    2-(2′-hydroxy-5′-n-dodecylphenyl)benzotriazole,    2-(2′-hydroxy-5′-sec-octyloxyphenyl)-5-phenylbenzotriazole,    2-(2′-hydroxy-3′-tert-amyl-5′-phenylphenyl-5-methoxybenzotriazole,    2-[2′-hydroxy-3′,5′-bis(α,α-dimethylbenzyl)-phenyl]benzotriazole and    like benzotriazole ultraviolet absorbers;-   2-(2′-Hydroxy-3′-dodecyl-5′-methylphenyl)benzotriazole,    2-(2′-hydroxy-3′-undecyl-5′-methylphenyl)benzotriazole,    2-(2′-hydroxy-3′-tridecyl-5′-methylphenyl)benzotriazole,    2-(2′-hydroxy-3′-tetradecyl-5′-methylphenyl)benzotriazole,    2-(2′-hydroxy-3′-pentadecyl-5′-methylphenyl)benzotriazole,    2-(2′-hydroxy-3′-hexaadecyl-5′-methylphenyl)benzotriazole,    2-[2′-hydroxy-4′-(2″-ethylhexyl)oxyphenyl]benzotriazole,    2-[2′-hydroxy-4′-(2″-ethylheptyl)oxyphenyl]benzotriazole,    2-[2′-hydroxy-4′-(2″-ethyloctyl)oxyphenyl]benzotriazole,    2-[2′-hydroxy-4′-(2″-propyloctyl)oxyphenyl]benzotriazole,    2-[2′-hydroxy-4′-(2″-propylheptyl)oxyphenyl]benzotriazole,    2-[2′-hydroxy-4′-(2″-propylhexyl)oxyphenyl]benzotriazole,    2-[2′-hydroxy-4′-(1″-ethylhexyl)oxyphenyl]benzotriazole,    2-[2′-hydroxy-4′-(1″-ethylheptyl)oxyphenyl]benzotriazole,    2-[2′-hydroxy-4′-(1″-ethyloctyl)oxyphenyl]benzotriazole,    2-[2′-hydroxy-4′-(1″-propyloctyl)oxyphenyl]benzotriazole,    2-[2′-hydroxy-4′-(1″-propylheptyl)oxyphenyl]benzotriazole,    2-[2′-hydroxy-4′-(1″-propylhexyl)oxyphenyl]benzotriazole,    2-(2′-hydroxy-3′-sec-butyl-5′-tert-butylphenyl)-5-n-butylbenzotriazole,    2-(2′-hydroxy-3′sec-butyl-5′-tert-butylphenyl)-5′-tert-pentylbenzotriazole,    2-(2′-hydroxy-3′-sec-butyl-5′-tert-butylphenyl)    5-n-pentylbenzotriazole,    2-(2′-hydroxy-3′-sec-butyl-5′-tert-pentylphenyl)-5′-tert-butylbenzotriazole,    2-(2′-hydroxy-3′-sec-butyl-5′-tert-pentylphenyl)-5′-n-butylbenzotriazole,    2-(2′-hydroxy-3′,5′-di-tert-butylphenyl)-5-sec-butylbenzotriazole,    2-(2′-hydroxy-3′,5′-di-tert-pentylphenyl)-5-sec-butylbenzotriazole,    2-(2′-hydroxy-3′-tert-butyl-5′-tert-pentylphenyl)-5-sec-butylbenzotriazole,    2-(2′-hydroxy-3,5′-di-sec-butylphenyl)-5-chlorobenzotriazole,    2-(2′-hydroxy-3,5′-di-sec-butylphenyl)-5-methoxybenzotriazole,    2-(2′-hydroxy-3,5′-di-sec-butylphenyl)-5-tert-butylbenzotriazole,    2-(2′-hydroxy-3,5′-di-sec-butylphenyl)-5-n-butylbenzotriazole,    octyl-5-tert-butyl-3-(5-chloro-2H-benzotriazole-2-yl)-4-hydroxybenzene    propionate, condensate of    methyl-3-[tert-butyl-5-(2H-benzotriazole-2-yl)-4-hydroxyphenyl]propionate    and polyethylene glycol (molecular weight: about 300) and like    benzotriazole ultraviolet absorbers.

The heat sensitive recording layer coating composition is applied to thesupport in an amount of about 1 to 10 g/m², preferably about 3 to 7 g/m²on a dry weight basis. The heat sensitive recording layer coatingcomposition may be applied to the support by a known coating device suchas a coating bar, a roll coater, an air knife coater, a blade coater, agravure coater, a die coater or a curtain coater.

If desired, an undercoat layer can also be provided between the supportand the heat sensitive recording layer in order to improve the thermalsensitivity and efficiency during recording. The undercoat layer isformed by coating the support with an undercoat layer coatingcomposition comprising as main components organic hollow particlesand/or an oil absorbing pigment and a binder and then drying thecoating.

Representative examples of oil absorbing pigments include clay, calcinedclay, amorphous silica, precipitated calcium carbonate and talc. Theaverage pigment diameter may be in the range 0.01 to 5 μm, preferablyfrom 0.02 to 3 μm.

Representative examples of organic hollow particles include particleshaving a shell made from an acrylic resin, styrene-based resin andvinylidene chloride-based resin and having a void ratio of about 50 to99%. The outside diameter of the organic hollow particle may be in therange 0.5 to 10 μm, preferably from 1 to 5 μm.

The organic hollow particles may be expandable hollow particles. Atypical example of such expandable hollow particles are microcapsuleshaving an average diameter of 0.1 to 5 μm comprising a vinylidenechloride resin shell and butane gas as fill material. When a supportcoated with an undercoat layer comprising such expandable hollowparticles is subjected to heat treatment, the microcapsules expand to anaverage particle diameter of 1 to 30 μm.

When the oil absorbing pigment is used in combination with the organichollow particles, the combined amount of the two components ispreferably about 40 to 90 weight-%, particularly about 50 to 80 weight-%based on the undercoat layer.

The binder used in the undercoat layer is selected from the binders tobe used in the heat sensitive recording layer and particularly preferredexamples are styrene-butadiene latex, a polyvinyl alcohol orstarch-vinyl acetate copolymer. The amount of binder to be used usuallyis in the range of about 5 to 30 weight-%, particularly 10 to 20weight-%, based on the undercoat layer.

The undercoat recording layer coating composition is applied to thesupport in an amount of about 2 to 20 g/m², preferably about 4 to 12g/m² on a dry weight basis.

If desired, a protective layer may be provided on the heat sensitiverecording layer to enhance the resistance of the recorded image to waterand chemicals, for example, oils, fats, alcohols, plasticisers and thelike to improve the runability during recording. The protective layer isformed by coating the heat sensitive recording layer with a protectivelayer coating composition comprising as main components a binder havingfilm-forming ability and optionally, a pigment and/or an insolubiliserand/or a lubricant and then drying the resulting coating film.

Representative examples of the binder to be used in the protective layercoating composition include polyvinyl alcohol (fully or partiallyhydrolysed), carboxy-modified polyvinyl alcohol, acetoacetyl-modifiedpolyvinyl alcohol, diacetone-modified polyvinyl alcohol,silicon-modified polyvinyl alcohol, starches, gelatine, caesin, gumarabic, derivatives of cellulose such as hydroxyethyl cellulose, methylcellulose, ethyl cellulose, carboxymethyl cellulose and acetylcellulose, starch vinyl acetate graft copolymers, styrene-maleicanhydride copolymers, methyl vinyl ether-maleic anhydride copolymers,isopropylene-maleic anhydride copolymers and like water-soluble resins,styrene-butadiene latex, acrylic latex, urethane latex and likewater-dispersible resins and mixtures thereof.

The pigment, insolubiliser, lubricant and, if required, otherauxiliaries may be selected from those used in the heat sensitiverecording layer coating composition.

The protective layer coating composition is applied in an amount ofabout 0.5 to 10 g/m², preferably about 1 to 5 g/m² on a dry weight basisand may be applied with a similar coating device to that used to coatthe heat sensitive layer.

It is also possible to provide a protective layer, an adhesive layer anda magnetic layer on the rear side of the support.

In particular the invention provides exceptional resistance toplasticiser, oil and heat ageing whilst showing improved backgroundwhiteness.

Non top coated heat sensitive recording materials prepared with thecompounds of the invention exhibit excellent printing characteristicswhen prepared by standard technologies, for example UV-offset andflexographic printing. Letterpress and dry-offset printing processes mayalso be used. Top coated heat sensitive recording materials preparedwith the compounds of the invention exhibit excellent printingcharacteristics. Further uses of the inventive recording materialsconcern conventional direct thermal printing (fax, point of salereceipts, tickets, labels, tags, plotter papers); two colour and mufticolour heat sensitive recording materials; and reversible heat sensitiverecording materials.

The following non-limiting examples Illustrate the novel materials ofthe present Invention.

EXAMPLES Example 1

10 g ofN-(p-toluenesulphonyl)-N′-(3-p-toluenesulphonyl-oxy-phenyl)urea—obtainedas described in example 4 of WO 00/35679—having crystal form A (see FIG.3) are slurried in toluene at 100° C. for 2 hours, and then cooled,isolated by filtration and dried in vacuo to give 9.5 g ofN-(p-toluenesulphonyl)-N′-(3-p-toluenesulphonyl-oxy-phenyl)urea havingan X-ray powder pattern having Bragg angles (2θ/CuK_(α)) of 10.3, 11.1,13.0, 13.3, 15.6, 17.1, 18.1, 18.4, 19.6, 20.0, 20.8, 21.3, 23.1, 25.0,25.5, 26.4, 26.8, 27.5, 29.1, 32.8.

Example 2

16 g ofN-p-toluenesulphonyl)-N′-(3-p-toluenesulphonyl-oxy-phenyl)urea—obtainedas described in example 4 of WO 00/35679 are slurried in 320 g ethylacetate at 20° C. for 0.5 hours, and then cooled, isolated by filtrationand dried in vacuo to give 9.6 g of N-(ptoluenesulphonyl)-N′-(3-p-toluenesulphonyl-oxy-phenyl)urea having anX-ray powder pattern having Bragg angles (2θ/CuK_(α)) of 6.4, 8.1, 10.1,11.1, 12.0, 12.7, 13.7, 15.7, 16.2, 16.5, 18.0, 19.2, 19.9, 20.5, 20.8,21.3, 21.8, 22.4, 22.6, 23.1, 24.1, 25.1, 25.6, 26.5, 26.8, 27.7, 28.6,28.8, 32.1.

Example 3

To a mixture of 100 g of toluene and 5 g of dimethylacetamide 13.2 g ofO-tosyl-m-aminophenol is added and the temperature adjusted to 50° C.Then 10.4 g of para-toluenesulphonyl isocyanate are added over 30minutes and the solution is allowed to stir at 50 to 60° C. for afurther 30 minutes. The reaction mass is then cooled to 15° C. andstirred for 30 minutes. Product is isolated by filtration and toluenewashing. After drying at 50° C.N-p-toluenesulphonyl-N′-3-p-toluenesulphonyloxyphenyl urea having anX-ray powder pattern having Bragg angles (2θ/CuK_(α)) of 10.3, 11.1,13.0, 13.3, 15.6, 17.1, 18.1, 18.4, 19.6, 20.0, 20.8, 21.3, 23.1, 25.0,25.5, 26.4, 26.8, 27.5, 29.1, 32.8 is isolated in 90% yield.

1. N-(p-toluenesulphonyl)-N′-(3-p-toluenesulphonyl-oxy-phenyl)ureahaving an X-ray powder pattern having Bragg angles (2θ/CuK_(α)) of 10.3,11.1, 13.0, 13.3, 15.6, 17.1, 18.1, 18.4, 19.6, 20.0, 20.8, 21.3, 23.1,25.0, 25.5, 26.4, 26.8, 27.5, 29.1, 32.8. 2.N-(p-toluenesulphonyl)-N′-(3-p-toluenesulphonyl-oxy-phenyl)urea havingan X-ray powder pattern having Bragg angles (2θ/CuK_(α)) of 6.4, 8.1,10.1, 11.1, 12.0, 12.7, 13.7, 15.7, 16.2, 16.5, 18.0, 19.2, 19.9, 20.5,20.8, 21.3, 21.8, 22.4, 22.6, 23.1, 24.1, 25.1, 25.6, 26.5, 26.8, 27.7,28.6, 28.8, 32.1.
 3. Process for the manufacture the compound accordingto claim 1, characterized in treatingN-(p-toluenesulphonyl)-N′-(3-p-toluenesulphonyl-oxy-phenyl)urea havingan X-ray powder pattern having Bragg angles (2θ/CuK_(α)) of 8.7, 9.7,12.1, 12.5, 13.8, 14.4, 16.8, 17.4, 18.4, 18.9, 19.6, 20.7, 21.2, 21.6,23.4, 24.4, 24.8, 25.2, 28.1, 28.8 with a solvent for a period in therange of 1 to 100 hours at a temperature in the range of 0 to 150° C.,then isolatingN-(p-toluenesulphonyl)-N′-(3-p-toluenesulphonyl-oxy-phenyl)urea. 4.Mixture of colour developers a) selected from the group consisting ofN-(p-toluenesulphonyl)-N′-(3-p-toluenesulphonyl-oxy-phenyl)urea havingan X-ray powder pattern having Bragg angles (2θ/CuK_(α)) of 10.3, 11.1,13.0, 13.3, 15.6, 17.1, 18.1, 18.4, 19.6, 20.0, 20.8, 21.3, 23.1, 25.0,25.5, 26.4, 26.8, 27.5, 29.1, 32.8, andN-(p-toluenesulphonyl)-N′-(3-p-toluenesulphonyl-oxy-phenyl)urea havingan X-ray powder pattern having Bragg angles (2θ/CuK_(α)) of 6.4, 8.1,10.1, 11.1, 12.0, 12.7, 13.7, 15.7, 16.2, 16.5, 18.0, 19.2, 19.9, 20.5,20.8, 21.3, 21.8, 22.4, 22.6, 23.1, 24.1, 25.1, 25.6, 26.5, 26.8, 27.7,28.6, 28.8, 32.1, and b)N-(p-toluenesulphonyl)-N′-(3-p-toluenesulphonyl-oxy-phenyl)urea havingan X-ray powder pattern having Bragg angles (2θ/CuK_(α)) of 8.7, 9.7,12.1, 12.5, 13.8, 14.4, 16.8, 17.4, 18.4, 18.9, 19.6, 20.7, 21.2, 21.6,23.4, 24.4, 24.8, 25.2, 28.1, 28.8.
 5. Mixture according to claim 4,further comprising a compound of formula II

wherein R¹ is C₁-C₂₀alkyl or C₆-C₁₀aryl, which can be substituted one tothree times with halogen, C₁-C₄alkyl, —NR²R³, wherein R² and R³independently from each other stand for hydrogen or C₁-C₈alkyl, orC₁-C₈acyl amino.
 6. A heat sensitive recording material, comprising thecompound of claim
 1. 7. A heat sensitive recording material according toclaim 6, further comprising at least one colour forming compound.
 8. Aheat sensitive recording material according to claim 1, wherein the heatsensitive recording material comprises at least one stabiliser. 9.Process for the manufacture the compound according to claim 2,characterized in treatingN-(p-toluenesulphonyl)-N′-(3-p-toluenesulphonyl-oxy-phenyl)urea havingan X-ray powder pattern having Bragg angles (2θ/CuK_(α)) of 8.7, 9.7,12.1, 12.5, 13.8, 14.4, 16.8, 17.4, 18.4, 18.9, 19.6, 20.7, 21.2, 21.6,23.4, 24.4, 24.8, 25.2, 28.1, 28.8 with a solvent for a period in therange of 1 to 100 hours at a temperature in the range of 0 to 150° C.,then isolatingN-(p-toluenesulphonyl)-N′-(3-p-toluenesulphonyl-oxy-phenyl)urea.
 10. Aheat sensitive recording material, comprising the compound of claim 2.11. A heat sensitive recording material, comprising the mixture of claim4.
 12. A heat sensitive recording material according to claim 11,further comprising a formula (II)

wherein R¹ is C₁-C₂₀alkyl or C₆-C₁₀aryl, which can be substituted one tothree times with halogen, C₁-C₄alkyl, —NR²R³, wherein R² and R³independently from each other stand for hydrogen or C₁-C₈alkyl, orC₁-C₈acyl amino.
 13. A heat sensitive recording material according toclaim 2, wherein the heat sensitive recording material comprises atleast one stabiliser.
 14. A heat sensitive recording material accordingto claim 4, wherein the heat sensitive recording material comprises atleast one stabiliser.
 15. A heat sensitive recording material accordingto claim 5, wherein the heat sensitive recording material comprises atleast one stabiliser.
 16. A heat sensitive recording material accordingto claim 10, further comprising at least one colour forming compound.17. A heat sensitive recording material according to claim 11, furthercomprising at least one colour forming compound.
 18. A heat sensitiverecording material according to claim 12, further comprising at leastone colour forming compound.